1. Field of the Invention
The present invention generally relates to the field of railroad brake pressure recording, and more particularly to a recorder which is plug compatible with both analogue and digital air brake pressure manifolds.
2. Description of the Prior Art
In the railroad industry, an air brake pressure manifold is used to report air brake pressure to the train operator. Historically, this pressure has been reported in terms of discrete, incremental reductions from the maximum pressure to which the train's brake system had been charged. A three digit binary code is used to designate seven discrete pressure reduction levels plus an emergency condition. A three conductor bus carries the binary coded pressure information to an operator display, which may be part of the manifold, and to three output pins to which a recorder external to the manifold can be connected.
Recently, so called analogue brake pressure manifolds have been proposed that measure and report the absolute air brake pressure over a continuous range. These manifolds employ a pressure to frequency convertor which, for example, may be calibrated so as to provide an output signal from zero to 100 Hz over a brake pressure range from zero to the maximum pressure to which the system will be charged.